The present invention relates to an apparatus and method for measuring and controlling fluid flow in a valve or passageway and, more particularly, to an apparatus and method for measuring and controlling fluid flow through a variable area flow orifice within the valve or duct.
Systems and methods for measuring and controlling fluid flow in a system are found in various industries. For example, various air distribution systems in commercial aircraft use various devices for measuring and controlling the flow of air through numerous branch lines that feed different portions of the aircraft. The flow of air through these branch lines may be controlled by a control valve, in response to a flow rate measurement.
The control valves presently known may be either mechanically complex or simple. One mechanically complex control valve may have a relatively heavy, complex, and expensive all mechanical servo valve that both measures and controls fluid flow rate. One mechanically simple control valve may have a simple, mechanical valve that is remotely actuated by a controller that uses either a venturi type flow sensor or a hot wire anemometer type flow sensor.
Although the above control valve schemes are generally acceptable, each has certain drawbacks. For example, the mechanically complex valve may have limited dynamic range and may be limited to one or two flow rate set points. The valve with a venturi type sensor may have limited dynamic range and may be relatively expensive. A hot wire anemometer may also be relatively expensive, may have poor accuracy, and may be limited to low temperature applications.
Hence, there is a need for an improved apparatus and method of controlling fluid flow through one or more branch lines of a system that addresses one or more of the above-noted drawbacks. Namely, an apparatus and method that is mechanically simple and/or relatively inexpensive, yet uses a flow measurement and control scheme that is accurate and/or is not unduly limited in its measurement range. The present invention addresses one or more of these needs.